α-二亚胺镍(Ⅱ)催化甲基丙烯酸甲酯聚合

以4种不同结构的α-二亚胺镍(Ⅱ)催化剂[(t-Bu)—N CH—CH N—(t-Bu)]NiBr₂(C1), [C₆H₅—N C(Me)—C(Me) N—C₆H₅]NiBr₂(C2), [(2,6-C₆H₃(Me)₂)—N C(Me)—C·(Me) N—(2,6-C₆H₃(Me)₂)]NiBr₂(C3)和[(2,6-C₆H₃(i-Pr)₂)—N C(An)—C(An) N—(2,6-C₆H₃(i-Pr)₂)]NiBr₂(An=acenaphthyl)(C4), 在甲基铝氧烷(MAO)作用下, 对甲基丙烯酸甲酯(MMA)进行催化聚合. 以C2为模型催化剂系统研究了Al/Ni摩尔比、 单体浓度、 聚合温度、 聚合时间和反应溶剂对催化活性及聚合物分子量的影响. 在较适合的聚合条件(催化剂用量为1.6 μmol, Al/Ni摩尔比为800, MMA浓度为2.9 mol/L, 甲苯为溶剂, 聚合温度为 60 ℃, 聚合时间为4 h)下, 讨论了催化剂结构对催化活性和聚合物分子量的影响. 研究发现, 催化剂C1~C3催化MMA聚合均得到富含间规结构的聚甲基丙烯酸甲酯(PMMA). 催化剂结构中空间位阻增大导致催化活性降低, 空间位阻最小的 C1催化活性最高[达107.8 kg/(mol Ni·h)]; 而空间位阻最大的C4催化活性仅为7.8 kg/(mol Ni·h). 催化剂结构中给电子效应增加有利于催化活性及聚合物分子量的增加. C2催化活性为62.5 kg/(mol Ni·h), 所得聚合物的分子量为5.0×10⁴; 而具有较强给电子效应的C3催化活性达到96.9 kg/(mol Ni·h), 并得到更高分子量的聚合物(7.6×10⁴).     

催化苯酚羟基化制邻、对苯二酚的研究进展

概述了苯酚双氧水羟基化催化剂的研究进展,指出水滑石类催化剂催化苯酚羟基化反应具有良好的应用前景,并对苯酚双氧水羟基化反应的影响因素和催化反应机理进行了讨论。     

中孔氧化硅负载铬催化剂上苯高选择性生成苯酚：响应曲面分析法用于反应条件优化

以硝酸铬为前驱体,中孔氧化硅SBA-16为载体,采用简单浸渍法制备了Cr/SBA-16催化剂,并采用广角和小角X射线衍射、N2吸附-脱附、透射电镜和紫外-可见光谱等技术对其进行了表征.同时将该催化剂用于以H2O2为氧化剂的苯直接羟基化制苯酚反应以考察其催化性能.将中心组合设计与响应曲面分析法(RSM)相结合,对影响反应性能的操作变量如反应温度、反应时间及H2O2和催化剂用量进行了优化.结果表明,独立变量和苯酚产率之间的关系可用二阶多项式模型来表达,其相关系数(R2)高达0.985,表明用RSM预测的数值与实验值吻合较好.得到的苯酚选择性较高时的操作条件为：反应温度324 K,反应时间8 h, H2O2和催化剂用量分别为3.28 mL和0.09 g.由此可见,将RSM法用于苯羟基化制苯酚反应条件优化是可靠的.     

活性炭催化苯一步羟基化制备苯酚(英文)

将市售活性炭经过硝酸、过氧化氢及不同温度进行处理后用于苯的羟基化反应,并研究了活性炭催化苯羟基化反应机理.用Boehm滴定,N2吸附-脱附及X射线光电子能谱对活性炭进行了表征.结果表明,反应体系的pH对催化剂活性具有重要的影响,活性炭对苯的吸附受表面含氧基团含量的影响.模型化合物反应结果表明,活性炭表面的酚羟基和羰基是反应的活性位,两者可相互转化,并在一定的pH条件下达到平衡,该转化使得H2O2活化为羟基自由基,进而与苯反应生成苯酚.在苯羟基化反应中,活性炭表现出良好且稳定的催化性能,苯酚收率可达14.4%.     

CuO+氧化苯直接形成苯酚反应机理的理论研究

在UB3LYP/6-31G(d,p) 水平下研究了CuO+氧化苯形成苯酚反应的详细机理,同时计算了单重态和三重态势能面。计算结果表明,苯与CuO+间相互作用主要为?配键,反馈?键较弱. CuO+氧化苯形成苯酚反应通过非自由基氢摘取机理完成,主要包括C-H键活化和苯基与羟基耦合两步反应. C-H键活化为整个反应的决速步骤. C-H键活化步骤涉及势能面交叉,且自旋交叉与动力学相关。CuO+氧化苯形成苯酚反应在气相中很容易进行.     

CuO/纳米载体催化苯酚羟基化反应

以CuO／纳米载体催化苯酚羟基化反应（30％H2O2为氧化剂）,考察了载体和CuO负载量对反应的影响。结果表明以纳米水滑石（HT）为载体的催化剂活性最高;以400℃下焙烧1h的CuO／HT为催化剂（苯酚质量的2％）,于75℃反应2h,苯酚的转化率为27．98％,双氧水的有效利用率达55．96％。     

几种载体载Ni催化剂上苯直接羟基化制备苯酚的研究

本文利用浸渍法制备了一系列不同载体的镍基催化剂,并将其用于苯的羟基化反应.用等离子原子直读光谱、粉末X射线衍射分析、比表面测试等对所制备的催化剂进行了表征.发现在所制备的催化剂中,以γ-Al2O3为载体的Ni1.7/γ-Al2O3 催化剂在苯的羟基化反应中具有相对较好的催化活性和选择性,而在Ni/TiO2和Ni/NaX上,则苯酚的深度氧化严重.     

La-Cu4FeAlCO3水滑石催化苯酚羟基化反应的动力学及反应机理

采用微波晶化法制取了La-Cu₄FeAlCO₃催化剂, 并通过XRD和IR手段对合成的化合物La-Cu₄FeAlCO₃进行了表征, 证明所得晶体为水滑石结构. 将催化剂La-Cu₄FeAlCO₃用于催化双氧水苯酚羟基化反应, 考察了反应时间、苯酚/双氧水摩尔比对苯酚羟基化的影响, 以及催化剂、苯酚、双氧水用量、反应温度与苯酚羟基化反应速率的关系. 结果表明: 在0.5 g苯酚、苯酚/双氧水(摩尔比)=1︰2, 0.025 g催化剂La-Cu₄FeAlCO₃、10 mL水为溶剂、反应温度为343 K, 反应120 min的反应条件下, 苯酚的转化率为50.09%. 且求出动力学方程为v=k[La-Cu₄FeAlCO₃] [C₆H₅OH][H₂O₂], 活化能E_a= 58.37 kJ/mol. 根据双氧水处理过的催化剂XPS表征结果, 得到了该反应机理为HO-Cu⁺-OH的过渡态自由基反应.     

负载型铁基复合氧化物催化苯酚羟基化的研究

在温和条件下对铁基复合氧化物催化苯酚和过氧化氢的羟基化反应进行了研究.结果表明,活性组分、载体以及催化剂/苯酚(质量比)、过氧化氢/苯酚(摩尔比)、反应温度和反应时间等对苯酚羟基化反应具有重要影响.Fe-A催化剂的活性组分形成了α-Fe2O3和尖晶石结构;Fe-B催化剂活性组分以非晶态分布在催化剂上,高度弥散,具有更好的催化性能.溶剂的加入,有助于苯酚和过氧化氢的混合,水是理想的羟基化反应溶剂,可以实现苯酚和过氧化氢水溶液的互溶,有利于·OH的生成.以Fe-B作催化剂,水为溶剂,反应温度65℃,反应时间1h,催化剂/苯酚(质量比)=0.02,水/苯酚(体积比)=2.0,过氧化氢/苯酚(摩尔比)=0.3,苯酚转化率21.6%,苯二酚选择性86.5%.     

Fe^3＋—阳离子交换树脂催化剂的制备及其催化性能的研究

本文研究了高分子催化剂—Fe3+－阳离子交换树脂在苯的羟基化合成苯酚反应中的应用。本催化剂具有操作简便、无腐蚀性,催化剂易从反应混合物中分离,并能重复使用等优点。     

THE INFLUENCE OF PRETREATMENT ON REFORMING SELECTIVITY OVER Pt-Re-A1_2O_3 AND Pt-Ir-Al_2O_3 CATALYSTS

In n-C_7~(?)reforming catalysis the selectivity of Pt-Ir-Al_2O_3 catalystis superior to that of Pt-Re-Al_2O_3 catalyst n-C_7~(?) shows deeper cracking onPt-Re-Al_2O_3 catalysts.Different reduction methods influence the selectivityof Pt-Re-Al_2O_3 catalyst.but have less influence on Pt-Ir-Al_2O_3 catalyst Thecracking activity and cracking depth of Pt-Re-Al_2O_3 catalyst deerease withthe water content present in the reduction process.     

Characterization of La-promoted Ni/Al2O3 catalysts for hydrogen production from glycerol dry reforming

In the current paper, dry (CO₂)-reforming of glycerol, a new reforming route, was carried out over alumina (Al₂O₃)-supported, non-promoted and lanthanum-promoted nickel (Ni) catalysts. Both sets of catalysts were synthesized via a wet co-impregnation procedure. Physicochemical characterization of the catalysts showed that the promoted catalyst possessed smaller metal crystallite size, hence higher metal dispersion compared to the virgin Ni/Al₂O₃ catalyst. This was also corroborated by the surface images captured by the FESEM analysis. From temperature-programmed calcination analysis, the derivative weight profiles revealed two peaks, which represent a water elimination peak at a temperature range of 373 to 473 K followed by nickel nitrate decomposition from 473 to 573 K. In addition, BET surface area measurements gave 85.0 m²·g⁻¹ for the non-promoted Ni catalyst, whilst the promoted catalysts showed an average of 1% to 6% improvement depending on the La loadings. Significantly, reaction studies at 873 K showed that glycerol dry reforming successfully produced H₂. The 2%La-Ni/Al₂O₃ catalyst, which possessed the largest BET surface area, gave an optimum H₂ generation (9.70%) at a glycerol conversion of 24.5%.     

Crystal‐Plane‐Controlled Selectivity of Cu2O Catalysts in Propylene Oxidation with Molecular Oxygen

The selective oxidation of propylene with O₂ to propylene oxide and acrolein is of great interest and importance. We report the crystal‐plane‐controlled selectivity of uniform capping‐ligand‐free Cu₂O octahedra, cubes, and rhombic dodecahedra in catalyzing propylene oxidation with O₂: Cu₂O octahedra exposing {111} crystal planes are most selective for acrolein; Cu₂O cubes exposing {100} crystal planes are most selective for CO₂; Cu₂O rhombic dodecahedra exposing {110} crystal planes are most selective for propylene oxide. One‐coordinated Cu on Cu₂O(111), three‐coordinated O on Cu₂O(110), and two‐coordinated O on Cu₂O(100) were identified as the catalytically active sites for the production of acrolein, propylene oxide, and CO₂, respectively. These results reveal that crystal‐plane engineering of oxide catalysts could be a useful strategy for developing selective catalysts and for gaining fundamental understanding of complex heterogeneous catalytic reactions at the molecular level.     

NiO-SiO2，NiO-Al2O3和NiO-Al2O3-SiO2催化剂上顺酐选择加氢性能的比较

以正硅酸乙酯和硝酸铝分别为硅源和铝源，硝酸镍为活性组分前驱物，采用溶胶-凝胶法制备了NiO-SiO2，NiO-Al2O3和NiO-Al2O3-SiO2催化剂。顺酐液相选择加氢活性和选择性评价结果表明：顺酐在三种催化剂上转化率都在99%以上，而产物的选择性有较大的差别，其中NiO-SiO2催化剂上γ-丁内酯的选择性达80.1%，NiO-Al2O3催化剂上丁二酸酐选择性达99%以上，NiOAl2O3SiO2催化剂上两种产物都有。XRD，TPR等体相结构和表面结构的表征说明，三种催化剂的相组成、NiO的分散性及与载体的相互作用存在明显差别，这些差别可能是造成不同选择加氢性能的原因。     

Hollow Nanotube Ru/Cu2+1O Supported on Copper Foam as a Bifunctional Catalyst for Overall Water Splitting

Hydrogen energy is considered as one of the ideal clean energies for solving the energy shortage and environmental issues, and developing highly efficient electrocatalysts for overall water splitting to produce hydrogen is still a huge challenge. Herein, for the first time, Ru-doped Cu₂₊₁O vertically arranged nanotube arrays in situ grown on Cu foam (Ru/Cu₂₊₁O NT/CuF) are reported and further investigated for their catalytic properties for overall water splitting. The Ru/Cu₂₊₁O NT/CuF presents ultrahigh catalytic activities for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline conditions, and it exhibits a small overpotential of 32 mV at 10 mA cm⁻² in the HER, and only needs 210 mV overpotential to achieve a current density of 10 mA cm⁻² in the OER. Importantly, the alkaline electrolyzer using Ru/Cu₂₊₁O NT/CuF as a bifunctional electrocatalyst only needs 1.53 V voltage to deliver a current density of 10 mA cm⁻², which is much lower than the benchmark of IrO₂(+)/Pt(−) counterpart (1.64 V at 10 mA cm⁻²). The excellent performance of the Ru/Cu₂₊₁O NT/CuF catalyst is attributed to its high conductive substrate and special Ru-doped nanotube structure, which provides a high electrochemical active surface area and 3D gas diffusion channel.     

The state of metals in the Pt/Al2O3 and (Pt-Cu)/Al2O3 catalysts as indicated by IR spectroscopy with isotope dilution of 12C16O with 13C18O molecules

Adsorption of ¹³C¹⁸O+¹²C¹⁶O mixtures on the Pt(2.9%)/γ-Al₂O₃, (Pt(2.6%)+Cu(2.7%))/γ-Al₂O₃, and (Pt(2.6%)+Cu(5.1%))/γ-Al₂O₃ catalysts was studied by FTIR spectroscopy. On the metallic Pt surface at coverages close to saturation, CO is adsorbed both strongly and weakly to form linear species for which the vibrational frequencies of the isolated ¹³C¹⁸O molecules adsorbed on Pt are ∼1940 and ∼1970 cm⁻¹, respectively. The redistribution of intensities of the high-and low-frequency absorption bands in the spectra of adsorbed ¹³C¹⁸O indicates that these linear forms are present on the adjacent metal sites. The weak adsorption is responsible for the fast isotope exchange between the gaseous CO and CO molecules adsorbed on metal. The Pt-Cu alloys, in which the electronic state of the surface Pt atoms characteristic of monometallic Pt remains unchanged, are formed on the surface of the reduced Pt-Cu bimetallic catalysts. The decrease in the vibrational frequencies of the isolated C=O bonds in the isolated Pt-CO complexes suggests that the CO molecules adsorbed on the Cu atoms affect the electronic properties of Pt. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 831–836, May, 2007.     

CS@Cu2O and magnetic Fe3O4@SiO2-pAMBA-CS-Cu2O as heterogeneous catalysts for CuAAC click reaction

The recovery of agricultural and food wastes are one of the main areas of current research for optimal biowaste management to reduce greenhouse gas (GHG) emissions that are generated when it is not properly treated. Corn silk (CS) as biowaste from the agricultural sector is a rich source of natural compounds especially polysaccharides. We present here a chemical activation method to convert CS to values added heterogeneous catalyst for the synthesis of triazoles compounds via copper catalyzed azide–alkyne cycloaddition (CuAAC) reaction. For this purpose, cuprous oxide coated CS (CS@Cu₂O) and multifunctional Fe₃O₄@SiO₂–para-aminomethyl benzoic acid–CS–Cu₂O composite (denoted as Fe₃O₄@SiO₂‐pAMBA-CS‐Cu₂O) were fabricated. Different analytical techniques have been used to describe the size, crystal structure, elemental composition and other physical properties of the fabricated catalysts. These heterogeneous catalysts showed excellent catalytic activities for the synthesis of 1,4-disubstituted-1,2,3-triazoles via click reaction in H₂O at 70 °C under base and external-reductant-free conditions. The magnetic properties of the catalyst allowed easy separation after reaction by simply applying an external magnet. Other advantages of this work are the recyclability of the catalyst, the absence of reducing agent and base, besides utilisation of bio wastes for the production of heterogeneous catalyst.     

H2O2-Na2S2O3反应对pH和反应物起始浓度比的依赖性

在H2O2-Na2S2O3反应体系中，pH值和[H2O2]0/[Na2S2O3]0对反应产物的浓度大小起着关键作用.本文通过考察这两种因素对反应产物的影响，以及对反应机理的模拟，得出了pH值和氧化剂与还原剂浓度比影响反应产物浓度的一般规律.结果表明：pH< 3时，反应主要生成单质硫， 3< pH< 6时， 较为稳定，提高pH和[H2O2]0/[Na2S2O3]0有利于SO42-生成，在中性或弱碱性溶液中S(Ⅳ)(HSO42-或SO32-)物质浓度出现峰值.     

电催化合成过氧化氢用于环境消毒

流行性疾病贯穿整个人类历史,伴随全球人口流动,它们可能演变成大型流行病.时至今日,我们仍在见证已知和新生的病原体对人类历史格局的改变.在与流行性疾病的抗争中,诸如紫外线辐射、巴氏杀菌和化学氧化法等技术被用于病原体的消杀和抗体的研制.然而,这些技术在环境消毒方面存在诸多不利,譬如过长的消杀时间、昂贵的特殊设备以及伴生的环境污染.过氧化氢是一种环境友好的多功能氧化剂,其分解的最终产物是氧气和水,广泛用于伤口消毒、纸浆和纺织品漂白、废水废气处理、化学合成、半导体清洗以及洗涤剂.目前,过氧化氢的生产严重依赖于传统的蒽醌法,该技术由Riedl和Pfleiderer于1939年提出,并沿用至今.然而,蒽醌法能耗高,该技术仅在较大规模上经济可行.不稳定的过氧化氢溶液存在危险性,这对大宗过氧化氢的运输和存储提出了额外的挑战.电化学合成过氧化氢被认为可有效替代传统蒽醌法,其反应条件温和,所需反应物是环境中广泛存在的水和氧气;与可再生能源相结合,有望实现分布式原位生产过氧化氢.过氧化氢既可以通过两电子的水氧化反应生成,又可以经由两电子的氧还原反应产生.Berl等在上世纪30年代首次报道了经由两电子的氧还原反应合成过氧化氢,并随后在1991年将其商业化(亦即Huron-Dow法).自此,Huron-Dow法被广泛用于纸浆和纸张的漂白过程.最近,Huron-Dow法进一步演变为电子-芬顿工艺,并被广泛用于饮用水净化和污水处理.目前,涉及高活性和高选择性的电化学合成过氧化氢的优秀综述见诸各大期刊;但是鲜有综述探讨该技术在环境消毒方面的应用.为了探寻提升公共卫生安全的有效替代方法,本文探讨了在电催化制备过氧化氢在环境消毒方面的可行性.本文涵盖三个主题,从基础理论到实践两个层次探讨了该技术在实际应用中的可行性.首先,回顾了H2O2消杀病原体的机理;其次,讨论了影响电催化制备过氧化氢的关键因素,并对现有的用于两电子水氧化和氧还原的催化剂进行了系统性的评述;最后,讨论了电极和电解池的合理设计,以实现电催化制备过氧化氢在实际中的应用.本文试图为最终实现电催化制备过氧化氢在环境消毒,尤其是公共卫生领域,提供可寻的研究方向.     

Effects of Carrier on CuO／TiO2 and CuO／Ti0.5Zr0.5O2 Catalysts in the NO＋CO Reaction

Using TiO2 and Ti0.5Zr0.5O2 as carriers, the CuO/TiO2 and CuO/Ti0.5Zr0.5O2 catalysts were prepared by the impregnation method with Cu(NO3)2 as active component. The catalytic activities in NO CO reaction were investigated using a microreactor-GC system, and structure and reducibility of catalysts were characterized by means of physical adsorption, TPR, XRD, NO-TPD technologies. It was found that the activity of CuO/Ti0.5Zr0.5O2 catalyst was higher than that of CuO/TiO2, probably due to the large specific surface area of Ti0.5Zr0.5O2 that played an important role in NO CO reaction.